Determination of furosine in dairy products by capillary zone electrophoresis: A comparison with the HPLC method

A procedure for determining furosine in milk and dairy products by capillary zone electrophoresis (CZE) with UV detection at 280 nm wavelength is described. The performance by CZE was compared with that of the IP-RP HPLC method in different samples of heat-treated milk and Mozzarella cheese. The hydrolyzed sample was dried under vacuum in order to remove the hydrochloric acid, dissolved with phosphate buffer at pH 8.0 and injected onto a fused-silica capillary (72 cm x 50 mu m i.d.). Furosine migration occurred without interference in approximately 6.5 min, with a signal-to-noise ratio of 5 for a 100 fmol peak. The CZE method gave a linear response (r = 0.997) for the furosine with the values ranging from those of pasteurized milk to those of indirect UHT milk, The repeatability (RSD < 3%) was close to that of the HPLC method, Nevertheless, a comparison between the 2 methods proved that low levels of furosine (from 5 to 12 mg/100 g protein) were underestimated by CZE, This limitation indicates that CZE of furosine is still not suitable for the official testing of pasteurized milk and Mozzarella cheese but, its rapidity and low cost of analysis, makes it attractive for routine in-house work.